1. Field of the Invention
This invention relates to methods of and apparatus for thermocompression bonding with a compensating system, and more particularly to methods of and apparatus for thermocompression bonding segments of lead frames to brittle substrates upon which circuits are formed, wherein an improved compensating system counteracts irregularities in the substrates.
This invention is suited for use in the manufacture of electronic components, such as integrated-circuit packages, hybrid integrated circuits and thin-film circuits. It is particularly suited for bonding lead frames to conductive patterns on glass or ceramic insulating substrates having various electronic components formed or bonded thereon. Such lead frames are conventionally used to connect such components into a variety of electronic equipment.
2. Description of the Prior Art
In the manufacture of electronic components, lead frames are bonded to conductive patterns formed on insulating glass or ceramic substrates. In so bonding the lead frames, it has long been recognized that a system of compensation is necessary to counteract irregularities in the glass or ceramic substrates to reduce their likelihood of cracking. (See, for example, U.S. Pat. Nos. 3,608,809 and 3,669,806 issued to R. H. Cushman; U.S. Pat. Nos. 3,804,319; 3,823,863 and RE 28,509 issued to B. Piechocki, all of which are assigned to assignee of of record.) The ceramic materials that are presently used in many substrates for thin-film and integrated circuits are often warped and nonuniform in thickness. Thermocompression bonding of lead frames to conductive patterns on such substrates produce highly localized forces and stresses. The result of these stresses on the nonuniform substrates is a certain degree of irreparable cracking of the substrates with the consequent loss of the entire circuits.
While various systems have provided the desired compensation to eliminate cracking of substrates, they have resulted in relative motion between the substrates and lateral guides that hold and align the substrates in an apparatus for thermocompression bonding the lead frames to the substrates. Since the substrates are usually formed of hard materials, such as alumina ceramics, this motion seriously damages the guides by the wearing action of the edges of the substrates on the guides. When the guides are so damaged, they loose their ability to position the substrates with the required precision in the bonding apparatus. Consequently, during bonding, the segments of the lead frame to be bonded to the substrates are not properly aligned with respect to conductive patterns on the substrates, and mechanically and electrically sound bonds cannot be consistently made. This results in the highly disadvantageous loss of manufacturing yield and an increase in the unit cost of the circuits.
Accordingly, it is desirable to provide compensation to prevent cracking of the substrates in combination with expedients to prevent relative motion between the substrates and their guides.
Moreover, it is desirable to effectuate the bonding at high speeds with minimum operator handling to increase the output of the operators and bonding apparatus.